Wanting to upgrade my fins (set on a thruster set-up) for my Vex Profusion 8'0 (8'0x29=115) I weight 79kg dry. I mainly use the board in larger swell 4-6/7/8ft. I was thinking Shapers S9s (5.19") but did not want to kill the board am worried that it will not be as loose. Was thinking 4.7"s rather but hard to find in futures. Any recommendations? Will the S9s work well without stiffening the board up to much? Cheers in advance.

Being from WA, you may be able to test the quobba fins? I have not fully tested them, but it looks like what you are after.

For your conditions, I am now using C-Drive fronts and standard central fin with some rake. But there a no C-drives in Future (yet?)